The U.S. Supreme Court will decide whether states may require a would-be voter to first prove citizenship — a case likely to answer larger questions about the sometimes conflicting roles of state and federal governments in regulating elections.

On Monday (October 15) the high court accepted an appeal from the State of Arizona, whose citizenship requirement was blocked by a federal appeals court, which said it conflicted with federal law.

The Arizona law, still winding through the legal system after passing as a ballot initiative in 2004, requires would-be voters to prove citizenship by presenting any one of a variety of documents during registration, including a driver’s license, passport, birth certificate or naturalization documents.

The state says the measure is needed to prevent noncitizens from voting. Minority and voting rights advocates have challenged the law, saying such fraud is rare and that the law puts undue burden on potential voters.

In April the 9th U.S. Circuit Court of Appeals in San Francisco blocked the law, saying it conflicted with the 1993 National Voter Registration Act (NVRA), which established a form that asks “Are you a citizen of the United States?” Voters check yes or no and sign the form.

The federal law “does not give states room to add their own requirements,” the split court ruled in the majority opinion.

Arizona, backed by several states, argues otherwise.

“The Arizona law does not interfere with Congress’s objectives in enacting the NVRA because requiring evidence of citizenship imposes a minimal burden on a limited number of persons and furthers the federal government’s and the States’ broad interest in protecting integrity of its election process,” Arizona argues in its petition.

In an amicus brief filed by Alabama, Georgia, Kansas and Texas, the states say they hold the constitutional authority to regulate voter registration and determine qualification.